Dear Xiaoyong
Have you tried Silcon nitride film (say LPCVD)?
bhat
Quoting Xiaoyong_Liu :

> Dear All,
>     I am making some of kind of  simple patterned wafer which will be used as
> test piece for our scanning sensor system. The requirement is that the sample
> needs to be protected by a passivation layer which is hardly able to be
> scratched since the sensor is in contact scanning. I tried to use SiO2 done
> by either PECVD or recative sputtering, but none of them works. I also tried
> photosensitive polymide material(PI 2771), but it is kind of soft aftere
> curing at 350C as suggsted by vendor. Does any one have any experience with
> that?